When I enquired about what you get for your money (£700) to have a towbar specified on a new F31 330d from my local BMW dealer. He said that the towbar wasn't an electric retractable version as the rear bodywork would foul its movement. But that the rear bodywork is modified to have a small access panel in it, to be able to access the towbar socket in the chassis. They also put in additional oil/water coolers to minimise the possibility of overheating when towing in hot weather. He couldn't tell me if the rear PDC is automatically disabled when the towbar is fitted. I believe this feature is available from other car manufacturers. So I guess I will have to wait and see about that one.